The second half hasn’t gone well for the Mets. They’re three games under .500 and have had a disastrous final month.

But for a few players, the post-All-Star break has been positive. And Jose Reyes is one of them.

With a kid like the 22-year-old Reyes, it’s important to see signs of growth and evolution as a player. You couldn’t look for a much better indication than Reyes’ second half. Unlike Braden Looper, he has successfully closed this season.

Entering last night, the Mets’ dazzling shortstop had posted a better batting average (.298 to .261), a higher on-base percentage (.336 to .284), more walks (14 to 12), fewer strikeouts (24 to 49) and fewer errors (three to 11) in the second half than he did in the first. That is progress; rapid progress.

“In the second half, I started to feel a lot more comfortable, and I started to see the ball better,” Reyes said yesterday. “I started to play better in the field too, so I play under control. Sometimes I try to be too quick with everything, rush a little bit. Now I started to learn how to slow down.”

Reyes, of course, is rarely in slow-down mode; when he runs, there is no more exciting player in New York. And few in baseball have run as well as Reyes this season. No Met has ever led the National League in stolen bases. Reyes is poised to break that streak and he just could end up topping the majors.

Reyes entered last night with 54 steals, three ahead of Florida’s Juan Pierre for the NL lead. He’s only two behind the White Sox’s Scott Podsednik for the major league lead.

“If I win, it’s good for me. I’m going to feel happy,” Reyes said. “But I’m not looking for that.”

Reyes then noted that his steals are supposed to benefit the team, not to garner individual accolades. The Mets have fallen out of contention, but Reyes’ special season is still worth noting.

No shortstop since 1900 has ever recorded 55 steals, 20 doubles, 15 triples and 90 runs in one season. Reyes has already reached three of those totals (he has 20 doubles, 16 triples and 90 runs), and he needs just one more steal to get to 55 and become the first shortstop in the modern era to reach that four-category plateau.

Reyes, who is also hitting .276 with seven homers and 56 RBIs, is pleased with the way his season has gone.

“I’m happy, man,” he said. “The most important thing is, I stay healthy this year. No injuries, nothing.”

Indeed, Reyes’ durability has probably been the biggest individual plus of the Mets’ season. He has played in a team-high 148 of the Mets’ 149 games.

“I’m still young,” said Reyes. “Still a lot of things to learn about this game. . . . I have to keep working on everything to get better and better and better every day.”

Reyes credited hitting coach Rick Down for helping to improve his hitting, noting that Down has told him, “When you got two strikes, make the pitcher throw the ball up.”

Reyes hits breaking balls well when they are strikes, Down said, but misses when he chases them low.

“He’ll hit with more power,” Down said, discussing the next step in Reyes’ evolution as a hitter. He added that Reyes must learn the right time in the count to become more aggressive with his power.

“He’s probably the best shortstop in baseball right now, tools-wise,” Down said. “With tools, who’s to say where he can go?”